U.S. patent application number 12/193524 was filed with the patent office on 2009-05-07 for boron nitride nanotube paste composition, electron emission source including the same, electron emission device including the electron emission source, and backlight unit and electron emission display device including the electron emission device.
Invention is credited to Young-Chul Choi, Kwang-Seok Jeong, Beom-Kwon Kim, Jong-Hwan Park.
Application Number | 20090115314 12/193524 |
Document ID | / |
Family ID | 40328269 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090115314 |
Kind Code |
A1 |
Choi; Young-Chul ; et
al. |
May 7, 2009 |
BORON NITRIDE NANOTUBE PASTE COMPOSITION, ELECTRON EMISSION SOURCE
INCLUDING THE SAME, ELECTRON EMISSION DEVICE INCLUDING THE ELECTRON
EMISSION SOURCE, AND BACKLIGHT UNIT AND ELECTRON EMISSION DISPLAY
DEVICE INCLUDING THE ELECTRON EMISSION DEVICE
Abstract
Boron nitride nanotube paste compositions, electron emission
sources including the same, electron emission devices including the
same and backlight units and electron emission display devices
including the same are provided. A boron nitride nanotube paste
composition includes about 100 parts by weight boron nitride
nanotubes, from about 500 to about 2000 parts by weight glass frit,
from about 1000 to about 2000 parts by weight filler, from about
2000 to about 4000 parts by weight organic solvent, and from about
4000 to about 6000 parts by weight polymer binder. Electron
emission devices including the boron nitride nanotube electron
emission sources have longer lifespan and improved uniformity among
pixels.
Inventors: |
Choi; Young-Chul; (Suwon-si,
KR) ; Park; Jong-Hwan; (Suwon-si, KR) ; Jeong;
Kwang-Seok; (Suwon-si, KR) ; Kim; Beom-Kwon;
(Suwon-si, KR) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
PO BOX 7068
PASADENA
CA
91109-7068
US
|
Family ID: |
40328269 |
Appl. No.: |
12/193524 |
Filed: |
August 18, 2008 |
Current U.S.
Class: |
313/503 ;
252/500; 252/514; 252/520.1; 252/520.3; 252/521.4 |
Current CPC
Class: |
H01J 1/304 20130101;
H01J 9/148 20130101; H01J 29/04 20130101; H01J 9/025 20130101; C03C
8/16 20130101; H01J 2201/30434 20130101; H01J 2201/30488 20130101;
B82Y 10/00 20130101; C03C 17/008 20130101 |
Class at
Publication: |
313/503 ;
252/500; 252/514; 252/520.1; 252/520.3; 252/521.4 |
International
Class: |
H01J 1/62 20060101
H01J001/62; H01B 1/12 20060101 H01B001/12; H01B 1/22 20060101
H01B001/22; H01B 1/02 20060101 H01B001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 1, 2007 |
KR |
10-2007-0111048 |
Claims
1. A boron nitride nanotube paste composition comprising: about 100
parts by weight boron nitride nanotubes, from about 500 to about
2000 parts by weight glass frit; from about 1000 to about 2000
parts by weight filler; from about 2000 to about 4000 parts by
weight organic solvent; and from about 4000 to about 6000 parts by
weight polymer binder.
2. The boron nitride nanotube paste composition of claim 1, wherein
a ratio of B to N of the boron nitride nanotubes ranges from about
1:0.5 to about 1:1.5.
3. The boron nitride nanotube paste composition of claim 2, wherein
the boron nitride nanotubes further comprise carbon.
4. The boron nitride nanotube paste composition of claim 3, wherein
a carbon content in the boron nitride nanotubes ranges from about
0.01 to about 100 parts by weight per 100 parts by weight
boron.
5. The boron nitride nanotube paste composition of claim 1, wherein
the filler is selected from the group consisting of Ag,
Al.sub.2O.sub.3, In.sub.2O.sub.3 and SnO.sub.2.
6. The boron nitride nanotube paste composition of claim 1, wherein
the organic solvent is selected from the group consisting of
terpineol, butyl carbitol acetate, and texanol.
7. The boron nitride nanotube paste composition of claim 1, wherein
the binder polymer is selected from the group consisting of methyl
methacrylate-methyl acrylic acid (MMA-MAA) and methyl
methacrylate-acrylic acid-polystyrene (MMA-AA-PS).
8. The boron nitride nanotube paste composition of claim 1, further
comprising an additive selected from the group consisting of
viscosity enhancers, leveling enhancers, dispersants, antifoaming
agents, and combinations thereof.
9. A boron nitride nanotube electron emission source comprising a
printed and calcined boron nanotube paste composition of claim
1.
10. An electron emission device comprising: a substrate; at least
one cathode on the substrate; at least one gate electrode
electrically insulated from the cathode; an insulator layer
insulating the cathode and the gate electrode; an electron emission
source hole exposing a part of the cathode; an electron emission
source in the electron emission hole and electrically connected to
the cathode, the electron emission source comprising about 100
parts by weight boron nitride nanotubes, from about 500 to about
2000 parts by weight glass frit, from about 1000 to about 2000
parts by weight filler, and from about 4000 to about 6000 parts by
weight polymer binder; and a phosphor layer opposing the electron
emission source.
11. The electron emission device of claim 10, wherein a specific
resistance of the device ranges from about 10.sup.-3 .OMEGA.cm to
about 10.sup.-8 .OMEGA.cm at 25.degree. C.
12. The electron emission device of claim 10, wherein a ratio of B
to N in the boron nitride nanotubes ranges from about 1:0.5 to
about 1:1.5.
13. The electron emission device of claim 12, wherein the boron
nitride nanotubes further comprise carbon.
14. The electron emission device of claim 13, wherein a carbon
content in the boron nitride nanotubes ranges from about 0.01 to
about 100 parts by weight per 100 parts by weight boron.
15. The electron emission device of claim 10, wherein the cathode
is patterned in a line pattern in parallel with the substrate.
16. The electron emission device of claim 10, further comprising a
gate electrode on the gate insulation layer.
17. An electron emission based backlight device comprising the
electron emission device of claim 10.
18. An electron emission display device comprising the electron
emission device of claim 10.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2007-0111048, filed on Nov. 1,
2007 in the Korean Intellectual Property Office, the entire content
of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to boron nitride nanotube
paste compositions, electron emission sources including the same,
electron emission devices including the electron emission sources,
and backlight units and electron emission display devices including
the electron emission devices.
[0004] 2. Description of the Related Art
[0005] Generally, electron emission devices are classified into two
types: 1) a hot cathode type in which a hot cathode is used as the
electron emission source, and 2) a cold cathode type in which a
cold cathode is used as the electron emission source. Examples of
cold cathode electron emission devices include Field Emitter Array
(FEA) devices, Surface Conduction Emitter (SCE) devices, Metal
Insulator Metal (MIM) devices and Metal Insulator Semiconductor
(MIS) devices, and Ballistic electron Surface Emitting (BSE)
devices.
[0006] Among these electron emission devices, carbon-type materials
are widely used as a constituent of the electron emission source.
For example, carbon nanotubes are widely used, which are superior
in conductivity, electro-focusing effects, and field emission
properties, and have low work functions.
[0007] However, since carbon nanotubes reach very high temperatures
when emitting electrons, combustion can occur in CO or CO.sub.2
even when there is a very small amount of oxygen, thereby burning
the ends of the carbon nanotubes. Moreover, properties, such as
band gap, change depending on the rolled direction of the carbon
nanotube, and since the rolling direction cannot be controlled, it
is not possible to control the properties of the conductor or
semiconductor. Hence, carbon nanotubes do not have good uniformity
or lifespan.
SUMMARY OF THE INVENTION
[0008] In one embodiment of the present invention, a boron nitride
nanotube paste composition has improved stability, lifespan, and
uniformity among pixels.
[0009] According to another embodiment of the present invention, a
boron nitride nanotube electron emission source is formed using the
boron nitride nanotube paste composition.
[0010] In yet another embodiment of the present invention, an
electron emission device has the boron nitride nanotube electron
emission source.
[0011] According to still another embodiment of the present
invention, a backlight device includes the electron emission
device.
[0012] In still yet another embodiment of the present invention, an
electron emission display device includes the electron emission
device.
[0013] According to one embodiment of the present invention, a
boron nitride nanotube paste composition comprises about 100 parts
by weight of boron nitride nanotubes, from about 500 to about 2000
parts by weight of glass frit, from about 1000 to about 2000 parts
by weight of filler, from about 2000 to about 4000 parts by weight
of an organic solvent, and from about 4000 to about 6000 parts by
weight of a polymer binder.
[0014] In one embodiment, the boron nitride nanotubes can have a
B-to-N ratio of about 1:0.5-1.5.
[0015] The boron nitride nanotube paste composition may also
include commonly used viscosity enhancers, leveling enhancers,
dispersants, and antifoaming agents whenever necessary.
[0016] According to another embodiment of the present invention, a
boron nitride nanotube electron emission source is formed by
printing and calcining the boron nitride nanotube paste composition
according to the invention.
[0017] According to yet another embodiment of the present
invention, an electron emission device comprises a substrate, a
cathode on the substrate, a gate electrode electrically insulated
from the cathode, an insulation layer insulating the cathode and
the gate electrode, an electron emission source hole exposing a
part of the cathode, an electrode emission source in the electron
emission source hole and electrically connected electrically to the
cathode, and a phosphor layer facing the electron emission source.
The electron emission source includes about 100 parts by weight of
boron nitride nanotubes, from about 500 to about 2000 parts by
weight of glass frit, from about 1000 to about 2000 parts by weight
of filler, and from about 4000 to about 6000 parts by weight of a
polymer binder.
[0018] The electron emission source can have a specific resistance
ranging from about 10.sup.-3 .OMEGA.cm to about 10.sup.-8 .OMEGA.cm
at 25.degree. C.
[0019] The electron emission device can include an additional gate
electrode on the upper surface of the gate insulation layer to form
a three-electrode structure.
[0020] According to another embodiment of the present invention, an
electron-emitting backlight device includes the electron emission
device.
[0021] According to still another embodiment of the present
invention, an electron emission display device includes the
electron emission device.
[0022] In one embodiment of the present invention, the electron
emission device includes an emitter including boron nitride
nanotubes instead of carbon nanotubes. The electron emission device
thus has a longer lifespan since deterioration (caused by
oxidation, which occurs when carbon nanotubes are used) does not
occur. Moreover, compared to conventional carbon nanotube emitters
(in which blinking occurs when operating an electron emission
device due to the inability of the carbon nanotubes to maintain
constant electric properties), the electron emission devices
according to the present invention have increased uniformity among
pixels due to the use of boron nitride nanotubes with constant
electric properties.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other features and advantages of the present
invention will become more apparent by reference to the following
detailed description when considered in conjunction with the
attached drawings in which:
[0024] FIGS. 1A to 1E are cross sectional views an electron
emission device taken at varying steps in a method of manufacturing
the electron emission device according to an embodiment of the
present invention;
[0025] FIG. 2 is a perspective view of an electron emission device
according to an embodiment of the present invention; and
[0026] FIG. 3 is a cross-sectional view of the electron emission
device of FIG. 2 taken along line II-II.
DETAILED DESCRIPTION OF THE INVENTION
[0027] According to one embodiment of the present invention, a
boron nitride nanotube paste composition includes about 100 parts
by weight of boron nitride nanotubes, from about 500 to about 2000
parts by weight of glass frit, from about 1000 to about 2000 parts
by weight of filler, from about 2000 to about 4000 parts by weight
of an organic solvent, and from about 4000 to about 6000 parts by
weight of a polymer binder.
[0028] Boron nitride nanotubes have the same structure as carbon
nanotubes, but because they do not react with oxygen, they have
higher stability and superior heat-resistance at high
temperatures.
[0029] The boron nitride nanotubes used in embodiments of the
present invention have the same structure as carbon nanotubes, but
carbons are randomly replaced with boron or nitrogen. This type of
boron nitride nanotubes may be composed solely of boron and
nitrogen, or may additionally include carbon.
[0030] In one embodiment, the boron nitride nanotubes may have a
content ratio of B and N ranging from about 1:0.5 to about 1:1.5.
When the content of N relative to B is lower than about 1:0.5, that
is, when the content of N is relatively small with respect to B,
structural instability arises. When the N content is higher than
1:1.5 relative to B, that is, when the content of N is relatively
large, low electron emission current density occurs.
[0031] Moreover, when the boron nitride nanotubes are composed of
B, N, and C, the boron nitride nanotubes may include about 100
parts by weight of boron to from about 0.01 to about 100 parts by
weight of carbon. Oxidation during electron emission occurs when
the carbon content is higher than about 100 parts by weight per
about 100 parts by weight of boron.
[0032] The boron nitride nanotubes can be synthesized using the
same manufacturing methods as for carbon nanotubes. For example,
arc discharge can be used for the synthesis. In such a method, a
hole is made in a graphite rod and filled with boron nitride
powder, and arc discharge is performed using the hole filled with
the boron nitride powder as an anode, thereby synthesizing
nanotubes including B, N, and C. If a tungsten rod is used instead
of a graphite rod, boron nitride nanotubes without C can be
synthesized.
[0033] Chemical vapor deposition can also be used to synthesize
boron nitride nanotubes. In this method, a catalytic metal such as
Ni, Co, Fe, or alloy thereof is mounted in a reactor and heated at
a temperature ranging from about 700 to about 900.degree. C. under
a gas atmosphere including a B-containing (e.g. BCl.sub.3) and a
N-containing gas (e.g. NH.sub.3), thereby synthesizing boron
nitride nanotubes.
[0034] According to one embodiment, a boron nitride nanotube paste
composition includes glass frit in an amount ranging from about 500
to about 2000 parts by weight. If the glass frit content is lower
than about 500 parts by weight per 100 parts by weight of the boron
nitride nanotubes, adhesiveness of the paste can be poor and
emission current density can be low. If the glass frit content is
greater than about 2000 parts by weight, viscosity becomes too
high, thereby causing printing difficulties and low emission
current density.
[0035] The filler, such as Ag, Al.sub.2O.sub.3, In.sub.2O.sub.3,
and SnO.sub.2, is used to improve the alignment properties of the
boron nitride nanotubes. In one embodiment, the filler is present
in an amount ranging from about 1000 to about 2000 parts by weight.
If the filler content is lower than about 1000 parts by weight per
100 parts by weight of the boron nitride nanotubes, the boron
nitride nanotubes are not arranged well during electron emission
source formation, leading to poor electron emission properties. If
the filler content exceeds about 2000 parts by weight, the
viscosity of the composition becomes exceedingly high, thereby
leading to printing difficulties.
[0036] The organic solvent is used to control the viscosity of the
composition, and terpineol, butyl carbitol acetate, toluene, or
texanol may be used as the organic solvent. Also, the organic
solvent may be present in an amount ranging from about 2000 to
about 4000 parts by weight per 100 parts by weight of the boron
nitride nanotubes. If the content of the organic solvent is lower
than about 2000 parts by weight, the viscosity of the composition
becomes too high to print. If the content of the organic solvent is
greater than about 4000 parts by weight, the viscosity of the
composition becomes too low to achieve appropriate printing
thickness.
[0037] The polymer binder, such as methyl methacrylate-methyl
acrylic acid (MMA-MAA) and methyl methacrylate-acrylic
acid-polystyrene (MMA-AA-PS), is used to increase the cohesion of
each component within the paste. The polymer binder may be present
in an amount ranging from about 4000 to about 6000 parts by weight
per 100 parts by weight of the boron nitride nanotubes. If the
polymer binder content is less than about 4000 parts by weight,
weak cohesion occurs, and when the binder polymer content is higher
than 6000 parts by weight, low printability and low electron
emission properties occur.
[0038] Moreover, the boron nitride nanotube paste composition
according to embodiments of the present invention can also include
viscosity enhancers, leveling enhancers, dispersants, and
antifoaming agents. The contents of the additives (such as
viscosity enhancers, leveling enhancers, dispersants, and
antifoaming agents) range from about 0 wt % to less than about 10
wt %. As the dispersant, commonly available surfactants and
antifoaming agents may be used.
[0039] A method of manufacturing the boron nitride nanotube paste
composition according to one embodiment of the present invention
will now be described. The boron nitride nanotube paste composition
according to embodiments of the present invention is used to form
an electron emission source, and may be made by first mixing the
boron nitride nanotube powder, the glass frit, and the filler
powder. When mixing the boron nitride nanotube powder and the glass
frit, a ball mill can be used to rotate the composition at a speed
ranging from about 5 to about 100 rpm for from about 1 to about 24
hours.
[0040] The polymer binder is separately prepared and diluted in an
organic solvent. As the organic solvent, terpineol, butyl carbitol
acetate (BCA), toluene, or texanol can be used. A dispersant can
also be added to the resin mixture. As the dispersant, commonly
used products, such as BYK-164 and Foamex 810 available from Tego
can be used, and the content of the dispersant may range from
greater than 0 wt % to lower than about 10 wt %.
[0041] First, the boron nitride nanotube powder and glass frit
mixture is combined with the polymer binder mixture and dispersed
to uniformly mix the boron nitride nanotube powder and glass frit
mixture with the resin mixture. An antifoaming agent can be added
in an amount ranging from about 0 to about 10 wt % to the boron
nitride nanotube powder, glass frit and resin mixture, and then a
dispersant may be added to the mixture in an amount ranging from
about 0 to about 10 wt %. The resulting mixture is stirred.
[0042] Next, an organic solvent is added to the boron nitride
nanotube paste composition in an amount sufficient to provide a
viscosity ranging from about 10,000 cP to about 50,000 cP.
Nonlimiting examples of suitable organic solvents include
terpineol, butyl carbitol acetate (BCA), toluene, and texanol. The
content of the organic solvent ranges from about 20 to about 40 wt
%. If the organic solvent content exceeds about 40 wt %, the
viscosity of the composition becomes too low to achieve appropriate
printing thickness.
[0043] According to another embodiment of the present invention, a
boron nitride nanotube electron emission source is made by printing
and calcining the boron nitride nanotube paste composition.
[0044] According to yet another embodiment of the present
invention, an electron emission device includes a substrate, a
cathode on the substrate, a gate electrode electrically insulated
from the cathode, an insulation layer insulating the cathode and
the gate electrode, an electron emission source hole exposing a
part of the cathode, an electrode emission source in the electron
emission source hole and electrically connected to the cathode, and
a phosphor layer facing the electron emission source. The electron
emission source includes about 100 parts by weight of boron nitride
nanotubes, from about 500 to about 2000 parts by weight of glass
frit, from about 1000 to about 2000 parts by weight of filler, and
from about 4000 to about 6000 parts by weight of a polymer
binder.
[0045] Generally, a conductor is used as an electron emission
source for the electron emission device, but the boron nitride
nanotubes according to embodiments of the present invention have
semi-conductive properties. Because of this, there is a risk of
lowering luminance, which can be compensated for by raising the
gate voltage. The voltage is a pulse voltage, and therefore does
not significantly affect cost.
[0046] The electron emission source according to embodiments of the
present invention, unlike carbon nanotubes, has semi-conductive
properties. The specific resistance can range from about 10.sup.-3
.OMEGA.cm to about 10.sup.-8 .OMEGA.cm at about 25.degree. C. In
one embodiment, the electron emission source includes boron nitride
nanotubes manufactured with the boron nitride nanotube paste
composition described above.
[0047] Therefore, the electron emission source according to
embodiments of the present invention has a specific resistance
ranging from about 10.sup.-3 .OMEGA.cm to about 10.sup.-8 .OMEGA.cm
at 25.degree. C. Also, the B to N content ratio of the boron
nitride nanotubes may range from about 1:0.5 to about 1:1.5.
Moreover, the boron nitride nanotubes for the electron emission
source can also include carbon. The carbon content may range from
about 0.01 to about 100 parts by weight per 100 parts by weight of
boron.
[0048] A paste method (generally used to apply a carbon nanotube
electron emission source on a cathode) can be used to manufacture
the boron nitride nanotube electron emission source according to
embodiments of the present invention. Here, instead of the carbon
nanotube paste composition, a boron nitride nanotube paste
composition according to embodiments of the present invention is
used. Hence, the boron nitride nanotube paste composition can be
printed and calcined to form a boron nitride nanotube electron
emission source on the cathode. The boron nitride nanotubes may be
single-walled and/or multi-walled.
[0049] For example, the boron nitride nanotube electron emission
source according to one embodiment of the present invention can be
made by first printing the boron nitride nanotube paste (prepared
as previously described) on the cathode to form a thick film, and
drying the film at a temperature ranging from about 90 to about
110.degree. C. for from about 10 minutes to about 1 hour.
[0050] Next, the thick film is exposed using a mask. Here, the
exposure energy may range from about 100 to about 20,000
mJ/cm.sup.2, and is adjustable depending on the desired thickness
of the film. The exposed film is developed in a 0.4 to 5% sodium
carbonate and acetone solution, or in ethanol, and the after-images
are removed using an ultrasonic cleaner.
[0051] The developed film is calcined under an air and nitrogen
atmosphere at a temperature ranging from about 400 to about
500.degree. C. for from about 10 to about 30 minutes to make a
boron nitride nanotube electron emission source. If the calcining
temperature is lower than about 400.degree. C., organic matter may
not be removed and glass frit may not dissolve, which is not
desirable.
[0052] FIGS. 1A to 1E are cross-sectional views of an electron
emission device at varying steps in a method of manufacturing an
electron emission device according to one embodiment of the present
invention. As shown in FIG. 1A, a cathode 11 is formed on a
substrate 10. For the substrate 10, a glass substrate can generally
be used. Also, the cathode 11 can be a transparent conductive
material such as indium tin oxide (ITO).
[0053] Specifically, the cathode layer is deposited on the
substrate 10 and patterned into a shape (such as a line shape) to
form the cathode 11. In one embodiment, the cathode has a line
shape.
[0054] As shown in FIG. 1B, an emitter layer is formed by
accumulating the emitter on the cathode 11. A boron nitride
nanotube electron emission source is used as the emitter layer.
Hence, the emitter layer is formed by applying the boron nitride
nanotube composition in paste form on the cathode 11.
[0055] After forming the emitter layer on the cathode 11, the
emitter is formed by patterning the emitter layer. The patterning
can be done according to well-known techniques. For example, a mask
(not shown) may be arranged in the lower part of the transparent
substrate 10 and UV light irradiated toward the transparent
substrate 10. The mask has a pre-shaped pattern. Therefore, when
the UV light is irradiated through the mask, the emitter layer is
photo-resistant according to the mask pattern. Lastly, after
washing the emitter layer with acetone, for example, the emitter 12
for the electron emission device (as shown in FIG. 1B) is
completed.
[0056] As shown in FIG. 1C, a photosensitive glass paste 13a is
applied over the emitter 12 on the surface of the substrate on
which the emitter 12 is formed. The rear surface of the resulting
matter (which is obtained by drying the surface of the substrate)
is then exposed. Accordingly, the photosensitive glass paste on the
upper part of the emitter remains unexposed, and the rest of the
photosensitive glass paste becomes the exposed area. Here, exposure
is performed at an intensity ranging from about 200 to about 500
mJ/cm.sup.2.
[0057] The photosensitive glass paste is a paste-type composition
containing glass powder, photosensitive resin, and solvent.
Nonlimiting examples of suitable glass powders include (1) lead
oxide, boric oxide, silicon oxide, calcium oxide
(PbO--B.sub.2O.sub.3--SiO.sub.2--CaO group) (2) zinc oxide, boric
oxide, silicon oxide (ZnO--B.sub.2O.sub.3--SiO.sub.2 group) (3)
lead oxide, boric oxide, silicon oxide, aluminum oxide
(PbO--B.sub.2O.sub.3--SiO.sub.2--Al.sub.2O.sub.3 group) (4) lead
oxide, zinc oxide, boric oxide, silicon oxide
(PbO--ZnO--B.sub.2O.sub.3--SiO.sub.2 group), and (5) lead oxide,
zinc oxide, boric oxide, silicon oxide, titanium oxide
(PbO--ZnO--B.sub.2O.sub.3--SiO.sub.2--TiO.sub.2 group). In
addition, inorganic oxide powders, such as aluminum oxides,
chromium oxides, and manganese oxides, can be mixed in the glass
powder.
[0058] The photosensitive resin is a material used for patterning
the electron emission source, and nonlimiting examples of the
photosensitive resin include pyrolytic acrylate-based monomers,
benzophenone-based monomers, acetophenone-based monomers, and
thioxanthone-based monomers. Specific nonlimiting examples include
epoxy acrylate, polyester acrylate, 2,4-diethyloxanthone, and
2,2-dimethoxy-2-phenylacetophenone.
[0059] The content of the photosensitive material may range from
about 3 to about 7 parts by weight per 100 parts by weight of glass
powder. If the photosensitive resin content is below about 3 parts
by weight per 100 parts by weight of glass powder, the exposure
sensitivity is poor. If the photosensitive resin content exceeds 7
parts by weight, development is not performed well, which is not
desirable.
[0060] For the solvent, at least one of butyl carbitol acetate
(BCA), terpineol (TP), toluene, texanol, and butyl carbitol (BC)
may be used. To maintain the viscosity of the paste composition
within a desirable range, the solvent is present in an amount
ranging from about 10 to about 20 parts by weight based on 100
parts by weight of glass powder. The solvent content can be
adjusted within this range to ensure efficient printing
performance.
[0061] The photosensitive glass paste can also include one or more
additives selected from photoinitiators, viscosity enhancers,
resolution enhancers, dispersants, and antifoaming agents. The
photoinitiator initiates cross-linking of the photosensitive resin
when the photosensitive resin is exposed. A non-limiting example of
a photoinitiator includes benzophenone.
[0062] After exposing the device depicted in FIG. 1C, the resultant
product is developed, and the unexposed area in the upper part of
the emitter layer is removed. The top part of the resulting product
is calcined and hardened at a temperature ranging from about 450 to
about 500.degree. C., thereby forming a gate insulation layer 13b
as shown in FIG. 1D.
[0063] By including an extra gate electrode on the top surface of
the gate insulation layer, the electron emission device according
to embodiments of the present invention can have a three-electrode
structure. As shown in FIG. 1E, the gate electrode 14 is formed on
the gate insulation layer 13b. The gate electrode 14 can have a
gate hole corresponding to the perforated hole on the top part of
the emitter, and can be formed by a thin-film process of deposition
and patterning of metallic materials, or a thick-film process of
screen printing of a metal paste.
[0064] The electron emission devices according to embodiments of
the present invention can be used in various electronic devices,
such as backlight devices for liquid crystal displays (LCDs), and
electron emission display devices.
[0065] According to one embodiment of the present invention, an
electron emission-based backlight device includes an electron
emission device according to an embodiment of the present
invention. The backlight device includes a top substrate and a
bottom substrate positioned in parallel and separated by a
distance, an anode formed on the top substrate, a phosphor layer
having a thickness formed on the anode, and an electron emission
device according to an embodiment of the present invention between
the top substrate and the bottom substrate.
[0066] The backlight device is operated by first applying a voltage
to the gate electrode, and then applying a voltage to the anode,
thereby causing electron emission from the electron emission
source. The emitted electrons emitted proceed toward the anode and
collide with the phosphor layer. Then, visible light is emitted
from the phosphor layer and passes through the top substrate and/or
the bottom substrate.
[0067] According to one embodiment of the present invention, an
electron emission display device includes the above described
electron emission device. FIG. 2 illustrates a top gate electron
emission display device, and FIG. 3 is a cross-sectional view of
the electron emission display device of FIG. 2 taken along line
II-II.
[0068] As shown in FIGS. 2 and 3, the electron emission display
device 100 includes an electron emission device 101 according to an
embodiment of the present invention and a front panel 102 aligned
in parallel with the electron emission device, which form a vacuum
luminescent space 103. A spacer 60 is also provided for keeping a
space between the electron emission device 101 and the front panel
102.
[0069] The electron emission device 101 includes a first substrate
110, gate electrodes 140 and cathodes 120 on the first substrate
110, and an insulation layer 130 between the gate electrodes 140
and the cathodes 120 to electrically insulate the gate electrodes
140 and the cathodes 120. The electron emission source holes 131
are formed in areas where gate electrodes 140 and cathodes 120
intersect, and electron emission sources 150 are disposed in the
holes 131.
[0070] The front panel 102 includes a second substrate 90, an anode
80 on the second substrate 90, and a phosphor layer 70 on the anode
80.
[0071] The electron emission display device is not limited to the
embodiments depicted in and described with reference to FIGS. 2 and
3, but may be modified in various ways such as including a second
insulation layer and/or additional focusing electrodes.
[0072] The following examples are presented for illustrative
purposes only, and do not limit the scope of the invention.
EXAMPLE
[0073] 2 g of boron nitride powder, 50 g of a polymer binder, 15 g
of In.sub.2O.sub.3 powder, 10 g of glass frit, and 3 g of BYK111 (a
dispersant) were added to 20 g of terpineol and stirred to form an
electron emission source forming paste composition.
[0074] An ITO cathode was patterned in lines on the glass
substrate. The electron emission source forming paste composition
was applied on the cathode and irradiated using a parallel exposing
unit at an exposure energy of 1000 mJ/cm.sup.2. Then, the substrate
was developed with acetone, and the electron emission source
forming composition was formed on the electron emission source
forming area.
[0075] A photoresist glass paste composition was applied on the
resulting material, and dried to form a photoresist glass paste
layer, which was irradiated from the back side of the substrate
using a parallel exposing unit at an energy of 300 mJ/cm.sup.2.
Then, the irradiated surface was developed using sodium carbonate
salt as an alkaline developing solution, and heat-treated at a
temperature of 500.degree. C. in an air gas atmosphere to form a
gate insulation layer. The gate electrode was formed on the gate
insulation layer (a material for the gate electrodes may be Cr, for
example) to prepare an electron emission device.
[0076] While the present invention has been illustrated and
described with reference to certain exemplary embodiments, it is
understood by those of ordinary skill in the art that various
modifications and changes to the described embodiments may be made
without departing from the spirit and scope of the present
invention as defined by the following claims.
* * * * *